Magnetic head and manufacturing method of the same, and magnetic recording / reproducing apparatus

ABSTRACT

A magnetic head comprises an MR element, and a substrate supporting the MR element from both sides at a center portion, and a magnetic tape is in contact and slide-contact with a slide-contact surface thereof. A curvature in a thickness direction of the slide-contact surface is set to be larger at a center portion than at both sides thereof. In this way, it is possible to protect the slide-contact surface of the magnetic head from eccentric wear and avoid deterioration of the magnetic head performance.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The present document is based on Japanese Priority Document JP2002-090430, filed in the Japanese Patent Office on Mar. 28, 2002, theentire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a magnetic head used forreproducing information from a tape-like magnetic recording mediumemployed in a VTR (video tape recorder), a digital VTR or the like, amethod of manufacturing the magnetic head, and a magneticrecording/reproducing apparatus employing the magnetic head.

[0004] 2. Description of the Related Art

[0005] In later years, with the progress in digitalization of imagesignals and computer-related technology, the amount of informationincreases exponentially. In a digital VTR or a tape streamer device foraccumulating, storing an reproducing such a large amount of information,in order to improve performance of a magnetic recording/reproducingsystem therein so as to deal the large amount of information at highspeed and promptly, research and development for providing the magneticrecording/reproducing system with a multi-head, a high-speed rotatingdrum, a narrow track, and a short wavelength have been made.

[0006] However, as for the inductive-type magnetic head which has beenused widely, since the magnetic resistance of the head cannot beunlimitedly reduced due to the limit of the capability of the headitself, for example, physical limit of the permeability of a magneticmaterial, it is quite difficult to largely improve a real densitythereof.

[0007] Therefore, it has been tried to utilize a magnetic head employingan MR element utilizing the magnetoresistive effect, in place of theconventional inductive head, in a magnetic recording/reproducingapparatus using a magnetic tape, such as a helical scan system.

[0008] By the way, as shown in FIG. 10, in a case of using a magnetichead 102 employing a shield-type MR element on a rotary head drum 101 ina magnetic recording/reproducing apparatus, a slide-contact surface 102a of the magnetic head 102 is exposed toward a magnetic tape 103, andthe magnetic tape 103 is in slide-contact with the slide contact surface102 a. Herein, an exposed amount δ of the slide-contact surface 102 a ofthe magnetic head 102 from an outer peripheral of the rotary head drum101 is called “head projection amount”. On the other hand, since outputintensity of the magnetic head 102 is substantially inverselyproportional to an MR head height h (refer to FIG. 6), the MR headheight is preferably as small as possible. Usually, the MR head heightis set in a range of 0.5-3 μm.

[0009] As shown in FIG. 11A, a curvature in a width direction of theslide-contact surface 102 a of the magnetic head 102 is formed to be Rx,while, as shown in FIG. 11B, a curvature in a thickness direction of theslide-contact surface 102 a of the magnetic head 102 is formed to be Ry.

SUMMARY OF THE INVENTION

[0010] In the magnetic recording/reproducing apparatus, as describedabove, since the magnetic tape 103 is in contact with and slides on theslide-contact surface 102 a of the magnetic head 102, the slide-contactsurface 102 a is worn away so that the magnetic head 102 cannot fullydemonstrate its intrinsic capability. Accordingly, there is a need forsuppressing wear of the slide-contact surface 102 a of the magnetic head102 to be as less as possible.

[0011] Tape tension and abrasive ability of the magnetic tape 103 affecton the wear of the slide-contact surface 102 a of the magnetic head 102.

[0012] As the magnetic tape 103, an MP tape (a metal particle tape) andan ME tape (metal-evaporated tape) are used. The MP tape is used in acondition of high tape tension owing to its characteristic feature, andhas high abrasive ability. On the other hand, the ME tape is used in acondition of low tape tension, compared with the MP tape, and has lowabrasive ability.

[0013] Accordingly, in a case of using the MP tape as the magnetic tape103, as shown in FIG. 12 with a double-dotted chained line, theslide-contact surface 102 a of the magnetic head 102 is worn away to bea similar figure to an initial shape along the curvature Ry.

[0014] On the other hand, as described above, the ME tape is used with alower tape tension and has less abrasive ability. Therefore, in a caseof using the ME tape as the magnetic tape 103, the wear of the magnetichead 102 is accelerated at a position where a head surface pressureincreases at around an entrance to the drum or an exit from the drum.The slide-contact surface 102 a of the magnetic head 102 is worn awaymore at a center portion thereof in relative to both side portionsthereof, as shown in FIG. 13 with a double-dotted chained line, that is,the slide-contact surface 102 a is eccentrically worn. This furtherdeteriorates the performance of the magnetic head 102.

[0015] As a method suppressing the wear of the slide-contact surface 102a of the magnetic head 102, there have been known not only a methodemploying a hard and less-wearing material for a head core or a shieldof the magnetic head but also a method employing a protective film forless wearing (as disclosed in Japanese Patent Application Publication2001-43215) and a method providing a groove in the vicinity of the headso as to have less surface pressure of the head (as disclosed inJapanese Patent Application Publication 2001-118220). However, when thehead surface is physically hardened or the groove is provided around thehead, the magnetic tape is more damaged at the time being in contactwith the head, which affects on durability of the magnetic tape.

[0016] In view of the above disadvantage, the present invention providesa magnetic head capable of suppressing deterioration of performanceowing to the eccentric wearing or the like, without hardening the headsurface physically and without providing a groove in the vicinity of thehead, and also provides a manufacturing method of the magnetic head anda magnetic recording/reproducing apparatus employing the magnetic head.

[0017] According to the present invention, with regard to the curvaturein the thickness direction of the slide-contact surface of the magnetichead, a curvature at the center portion is set to be larger than acurvature of the both side portions. Thus, the wear of the centerportion at an initial period is eliminated so that the deterioration inthe performance of the magnetic head can be avoided.

[0018] The following effects may be obtained in accordance with thepresent invention:

[0019] (1) The present invention reduces the wear, especially, eccentricwear of the magnetic head and avoids deterioration of magnetic headperformance without providing a protective film on the magnetic head, asin the conventional example;

[0020] (2) The spacing between the magnetic tape and the MR elementaccording to the present invention prevents the MR element from beingworn away;

[0021] (3) The tape tension of the magnetic tape per tape width set toapproximately 0.5-1.0 gf/mm at around the entrance to the drum inaccordance with the present invention suppresses the wear of themagnetic head by the magnetic tape at around the entrance to the drum;and

[0022] (4) According to the method of the present invention, themagnetic head with a plurality of curvatures in the thickness directionof the slide-contact surface can be formed using a several kinds ofabrasive containing lapping tape each having different stiffness. First,the slide-contact surface of the magnetic head is lapped using a lappingtape with low stiffness and, next, the slide-contact surface is lappedusing a lapping tape with high stiffness. This enables the lapping in asequential order from the part with the smaller curvature at the outerside to the part with the larger curvature at the inner side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of thepresent invention will become more apparent from the followingdescription of the presently preferred exemplary embodiments of theinvention taken in conjunction with the accompanying drawings, in which:

[0024]FIG. 1 is a perspective view of a magnetic head.

[0025]FIG. 2A is a front view of the magnetic head in a width direction,and FIG. 2B is a front view of the magnetic head in a thicknessdirection.

[0026]FIG. 3 is an enlarged view of a main part of the magnetic head ofFIG. 2B.

[0027]FIG. 4 is a perspective view of a rotary head drum.

[0028]FIG. 5 is a plan view of a recording/reproducing apparatus.

[0029]FIG. 6 is a view explaining relationship between an MR head and amagnetic tape.

[0030]FIG. 7 is a graph showing an effect of the magnetic head of thepresent invention in comparison with a conventional magnetic head.

[0031]FIG. 8 is a plan view of a lapping machine.

[0032]FIG. 9 is an enlarged view of a main part of a magnetic head ofanother embodiment.

[0033]FIG. 10 is a plan view of a conventional example.

[0034]FIG. 11A is a front view of the magnetic head of the conventionalexample in a width direction, and FIG. 11B is a front view of themagnetic head in a thickness direction.

[0035]FIG. 12 is a view explaining a state where the magnetic head ofthe conventional example is worn away in a case of using an MP tape asthe magnetic tape.

[0036]FIG. 13 is a view explaining a state where the magnetic head ofthe conventional example is worn away in a case of using an ME tape asthe magnetic tape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Now, the present invention is explained with reference to theattached drawings. FIG. 1 is a perspective view showing a magnetic head(hereinafter, referred to as MR head) 1. The MR head 1 comprises an MRelement 2 and a substrate 3 which supports the MR element 2 at a headgap portion G at the center thereof from both sides. A magnetic tape 5comes in contact with and slides on a slide-contact surface 4 of the MRhead 1. As shown in FIG. 2A, the slide-contact surface 4 of the MR head1 is formed to have a uniform curvature Rx in a width direction. Inaddition, as shown in FIG. 2B and enlargedly shown in FIG. 3, acurvature Ry in a thickness direction of the slide-contact surface 4comprises a plurality of large and small curvatures. A curvature Ry 2 ata center portion thereof is set to be larger than a curvature Ry1 atboth side portions. For example, the curvature Ry1 at the both sideportions is formed to be 0.5-3 mm and the curvature Ry2 at the centerportion is formed to be 5 mm to ∞.

[0038] As shown in FIG. 4, the MR head 1 is attached to a rotary drum 12of a magnetic recording/reproducing apparatus 11, which will bedescribed next, as a reproducing head. The rotary head drum 12 comprisesa rotating upper drum 12 a and a fixed lower drum 12 b. The reproducingMR head 1 and a recording magnetic head 6 are positioned to have a phaseof 90° to each other between the upper drum 12 a and the lower drum 12b. The rotary head drum rotates in a state slanted with a predeterminedangle.

[0039] As shown in FIG. 5, the magnetic recording/reproducing apparatus11 includes the rotary head drum 12, a pair of inclined posts 13 a and13 b, which wind the magnetic tape 5 on an outer peripheral surface ofthe rotary head drum 12 with a predetermined winding angle, a pluralityof tape guides 14 a-14 d, a pinch roller 15, a capstan 16, a tensionroller 17, a tape supply reel 18 and a tape take-up reel 19. Themagnetic tape 5 taken out from the tape supply reel 18 runs along theouter peripheral surface of the rotary head drum 12 in an inclinedcondition by the pinch roller 15 and the capstan 16, and then is woundaround the tape take-up reel 19.

[0040] As shown in FIG. 6, the MR element 2 and the magnetic tape 5which is in slide-contact with the slide-contact surface 4 of the MRhead 1 have a fixed spacing S therebetween. In addition, the magnetictape 5 is set to have a tape tension of 0.5-1.0 gf/mm per magnetic tapewidth in the vicinity of an entrance to the rotary head drum, and a headprojection amount of 5-30 μm.

[0041] Next, the operation of the MR head 1 and a magneticrecording/reproducing apparatus 11 will be described. As describedabove, in the present embodiment, with regard to the curvature Ry in thethickness direction of the slide-contact surface, the curvature Ry2 atthe center portion of the slide-contact surface 4 is set larger than thecurvature Ry1 at the both side portions. Therefore, the portion around ahead gap at the center portion of the MR head 1 comes into contact withthe magnetic tape 5 at around the entrance to and the exit from therotary head drum, while the MR head 1 does not heavily contact themagnetic tape 5 at a portion other than around the entrance to and theexit from the rotary head drum. Accordingly, the wear of the MR head 1can be largely suppressed. The operation of suppressing wearing becomessignificant as the magnetic tape 5 becomes thinner and lowers itsstiffness. Accordingly, the present invention is more effective whenapplied for a thinner and larger-capacity magnetic tape.

[0042]FIG. 7 shows an experimental result in which an initial wornamount in a case of setting the curvature Ry2 at the center portionlarger than the curvature Ry1 of the both side portions is compared thean initial worn amount in a case of uniformly setting a curvature in thethickness direction. From the result, it was proved that the initialworn amount of the MR head 1 of the present invention was largelyimproved compared with the conventional example.

[0043] Next, a manufacturing apparatus (lapping machine) and amanufacturing method (lapping method) of the MR head 1 described above.

[0044]FIG. 8 is a summarized plan view of a manufacturing apparatus(hereinafter, referred to as lapping machine) 21 of the MR head 1. Thelapping machine 21 includes a rotary drum 22 to which a plurality ofuntapped MR heads 1 as targets to be lapped are attached, a head lappingtape 23 which is wound and runs around the rotary drum 22 with apredetermined winding angle, and a tape feeder mechanism 24.

[0045] The tape feeder mechanism 24 includes a tape supply reel 25 and atape take-up reel 26 and a plurality of tape guides 27. In accordancewith the difference between the rotational speed of the tape supply reel25 and the tape take-up reel 26, the tape tension of the head lappingtape 23 can be changed.

[0046] The rotary drum 22 is formed substantially similar to the rotaryhead drum 12 of the magnetic recording/reproducing apparatus 11. Theplurality of untapped MR heads 1 are detachably attached so that theslide-contact surfaces 4 thereof are projected from the outer peripheralsurface of the drum. On the other hand, the head lapping tape 23 isformed by adhering an abrasion material on a surface of a base layer ofPET (Polyethylene terephthalate).

[0047] The base layer of the head lapping tape 23 is formed to have athickness in a range of 10-50 μm, and head lapping tapes 23 of severalthickness for the base layer thereof are prepared in advance.

[0048] Next, the method of manufacturing the MR head 1 using the lappingmachine 21 will be explained. In the present method, first of all, apart with a small curvature Ry1 is lapped and formed, and, a part with alarge curvature Ry2 is lapped and formed subsequently.

[0049] The part with the small curvature Ry1 is formed by lapping theslide-contact surface 4 of the not-yet-lapped MR head 1, that is, thelapping target, using the head lapping tape 23 having a base layerthickness of 15 μm at a tape tension of 30 gf/mm. After forming the partwith the small curvature Ry1, the part with the large curvature Ry2 isformed by lapping the slide-contact surface 4 of the MR head 1 usinganother head lapping tape 23 having a base layer thickness of 30 μm at atape tension of 15 gf/mm.

[0050] In this way, it is possible to form the part with the smallcurvature Ry1 and the part with the large curvature Ry2 in a sequentialorder by varying the thickness of the base layer, that is, the tapestiffness, of the head lapping tape 23 and the tape tension thereof. Inaddition, it is also possible to form any desired curvature byappropriately changing the base layer thickness and the tape tension ofthe head lapping tape 23.

[0051] It is also possible to form the part with the large curvature Ry2not by lapping with the lapping machine 21 but by adjusting the tapetension of the magnetic tape in the similar way to the case of thelapping machine 21, and lapping the MR head 1 after it is built in themagnetic recording/reproducing apparatus, such as a VTR or a streamer.In this case, it is necessary to take the lapping amount inconsideration and to form of the part with the small curvature Ry1 tohave a relatively large height. In the above embodiment, the case withtwo curvatures has been described. However, as shown in FIG. 9, theremay be three or more curvatures in ascending order from an outer side tothe center. In this case, the MR head 1 is formed from the part with thesmall curvature, positioned at the outer side, to the part with thelarge curvature, positioned at the inner side.

[0052] In the present embodiments, the case where a plurality ofcurvatures are provided in the thickness direction has been described.However, if necessary, there may be provided a plurality of curvaturesin the width direction instead of the thickness direction.

[0053] Although the invention has been described in its preferred formwith a certain degree of particularity, obviously many changes andvariations are possible therein. It is therefore to be understood thatthe present invention may be practiced otherwise than as specificallydescribed herein without departing from the scope and the sprit thereof.

What is claimed is:
 1. A magnetic head comprising an MR element and asubstrate supporting the MR element from both sides thereof at a centerportion, in which a magnetic tape is in contact and slide-contact with aslide-contact surface, wherein: a curvature in a thickness direction ofsaid slide-contact surface is set to be larger at a center thereof thanat both sides.
 2. The magnetic head according to claim 1, wherein: saidmagnetic head is mounted on a rotary drum and is used for reproducinginformation recorded on the magnetic tape.
 3. A magnetic head comprisingan MR element and a substrate supporting the MR element from both sidesthereof, in which a magnetic tape is in contact and slide-contact with aslide-contact surface thereof, wherein: the magnetic tape which is inslide-contact with the slide-contact surface and the MR element have afixed spacing therebetween.
 4. The magnetic head according to claim 3,wherein: said magnetic head is mounted on a rotary drum and is used forreproducing information recorded on the magnetic tape.
 5. A magneticrecording/reproducing apparatus including a rotary drum having arecording magnetic head and a reproducing magnetic head, wherein: saidreproducing magnetic head comprises an MR element, and a substratesupporting the MR element from both sides at a center portion, and amagnetic tape is in contact and slide-contact with a slide-contactsurface thereof, and a curvature in a thickness direction of saidslide-contact surface is set to be larger at a center portion than atboth sides thereof
 6. The magnetic recording/reproducing apparatusaccording to claim 5, wherein: said magnetic recording/reproducingapparatus is arranged so that the magnetic tape has a tape tension permagnetic tape width in the vicinity of a rotary drum entrance of 0.5-1.0gf/mm and a head projection amount of 5-30 μm.
 7. A method ofmanufacturing a magnetic head in which a magnetic head as a lappingtarget is attached to a rotary drum, a lapping tape is wound around therotary drum with a predetermined angle, and a slide-contact surface ofthe magnetic head is lapped to have a plurality of curvatures in athickness direction using the lapping tape, said method comprising:first, lapping the slide-contact surface with a lapping tape with a lowstiffness so as to form a part with a small curvature, and next, lappingthe slide-contact surface with a lapping tape with a high stiffness soas to form a part with a large curvature.
 8. The method of manufacturinga magnetic head according to claim 7, wherein: said magnetic headcomprises an MR element, and a substrate supporting the MR element fromboth sides at a center portion, and a magnetic tape is in contact andslide-contact with a slide-contact surface thereof, and said magnetichead is mounted on a rotary drum and is used for reproducing informationrecorded on the magnetic tape.